Hi Sue. In my opinion the more expensive GPS models are not necessarily better, they just have more features. If you don't need Bluetooth, an mp3 player or photo storage on your GPS, there's no need to pay more than $300.
The Tom Tom One an Garmin Nuvi 200 are very good basic models that work well right out of the box, have all the basic features including voice prompts, and shouldn't cost more than $300.
The only feature I would spend more for is a larger screen if that's important to you.
You have to think about how you are going to use the device. I use mine 80% of the time when I'm in a rented car when I travel. So portability is important. I rarely use it in my own car because I use the car mostly to go to the same places.
By the way, once you get one you can't believe how you ever got by without one. It has saved me hours of getting directions to places. Good luck. Tom.